LED chip is the heart of the LED display
, and other products, the main function is to convert electrical energy to light energy, in use process, the LED chip, also can appear all sorts of problems, now let small make up take you look at the LED chip with conventional will appear that six big problem!
01 forward voltage reduction, dark (
Is a kind of electrode and luminescent material as ohmic contact, the contact resistance is big, mainly caused by the low substrate concentration or electrode material defect.
Is a kind of electrode and materials for non-ohmic contacts, mainly in the first layer electrode chip electrode preparation process of evaporation of extrusion is printed or clip, distribution position.
Encapsulation process also may cause a positive pressure is reduced, the main reason with silver adhesive curing insufficient, bracket or chip electrode contact resistance caused by contamination such as large and unstable contact resistance.
Low forward voltage chip in a fixed voltage test, by the chip's current is small, which show dark spots, and a dim light phenomenon is the chip itself luminous efficiency is low, positive pressure drop to normal.
02 hard pressure welding (
Won't stick: mainly because the electrode surface oxidation or have glue (
Have not firm contact with luminescent material and welding line layer not firm, which is given priority to with thickening layer falls off.
Through electrode, is often associated with chip material, material brittle and strength is not high to break through the electrode, general GAALAS materials (
Such as high, infrared chips)
The electrode material GAP is easy wear.
Bonding debugging should from the welding temperature, ultrasonic power, ultrasonic time, pressure, golden ball size, to adjust the bracket positioning etc.
03 luminous color difference (
Have obvious difference with a chip light-emitting color problems, mainly because of epitaxial wafer materials ALGAINP four element material using quantum structure is very thin, it is hard to guarantee the regional growth components.
Component decided to forbidden band width and forbidden band width wavelength)
GAP yellow green chip, light wavelength does not have a large deviation, but due to the human eye is sensitive to the band color, is easy to detect yellow and green.
Because the wavelength is determined epitaxial wafer materials, the smaller the area, a concept of color deviation is smaller, so the adjacent selection method in M/T work.
GAP some light color is more orange red chip, this is due to its luminescent mechanism for indirectly by leaps.
Influenced by impurity concentration, current density increased, easy to produce the impurity level offset and glowing saturation, light is turning into a orange.
04 brake fluid effect (
Is a light emitting diode under normal voltage can't conduction, when the voltage is raised to a certain extent, current mutations.
Cause brake fluid phenomenon is appeared when luminescence material growth of epitaxial wafer reverse intercalation, there is the phenomenon of the LED in the IF = 20 ma test positive pressure drop when the hidden, in use process is out of the poles voltage is not big enough to show is not bright, available information instrument from the transistor tracer testing curve, but can be by small current IF = 10 ua under positive pressure drop to found that small electrical flow of large, positive pressure drop may be due to the problem.
05 IR reverse leakage current under the condition of limited for the basic characteristic of the diode reverse leakage current, according to the provisions of the LED before regular refers to reverse voltage at 5 v reverse leakage current.
With the improvement of the performance of the light emitting diode, a reverse leakage flows more and more small.
is typically used in series, in parallel to join, to adapt to different working voltage, the series of LED lights the more the greater the influence, as long as one of the LED lights inside the attachment open circuit, will cause the series circuit of the whole series of LED light is not on, is this kind of situation is more serious than the first kind of circumstance.
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